#define _CRT_SECURE_NO_WARNINGS 1
#include <iostream>
using namespace std;

int main() {
    int n;
    scanf("%d", &n);
    int arr[32];
    int count = n;
    count--;
    arr[0] = 1;
    arr[1] = 1;
    while (count)
    {
        if (count >= 2)
            for (int i = count - 2; i >= 0; i--)
            {
                arr[count] += arr[i];
            }
        count--;
    }
    int sum = 0;
    for (int i = 0; i < n; i++)
        sum += arr[i];
    printf("%d", sum);
    return 0;
}